RHYNCHONELLA. 79 



Plate X, fig. 17. A fragment of the beak (enlarged) to illustrate the tubular expansion 



of the deltidium. 

 „ fig. 14. Interior of the dorsal valve, from a specimen in the British Museum. 

 ,, fig. 15. Interior of the ventral valve, ib. 



„ figs. 43, 44. Var. Woochoardii, from the Chalk of Norwich, in the collec- 

 tion of Mr. Fitch, 

 figs. 45, 46. Ib. From the Chalk of Charing, in the cabinet of Mr. Harris. 



35. Rhynchonella lbibata, Schlotheim, Sp. PI. XII, figs. 1 — 5. 



Terebratulites lijibatus, Schlotheim. Leonhard's Tasb., vol. vii, p. 113, 1813; 



Petrjk. i, 286, reference Faujas, Mont St. Pierre, 



pi. xx vi, fig. 4, 1799. 

 Terebratula sub-plicata, Mantel!. Fossils of the South Downs, p. 211, tab. xxvi, 



fig. 5, 1822. 



— — Woudward. A Synoptical Table of Brit. Org. Remains, 



p. 22, 1830. 



— lentiformis, Woodioard. Geol. of Norfolk, tab. vi, fig. 11, 1833. 



— subplicata and lentiformis, Morris. Catalogue, 1843. 

 Rhynchonella subplicata, D'Orbigny. Pal. Franc., Terrains Cretaces, vol. iv, p. 48, 



pi. 499, figs. 13 — 17 (under the false name of Bhyn. 

 dutempleana), 1847. 

 Terebratula limbata, Bronn. Index Pal., vol. 2, p. 1246, 1848. 



Diagnosis. Shell more or less transversely oval; somewhat trigonal or circular 

 when young ; beak short, narrow, and incurved ; foramen minute, close under the 

 acute extremity of the beak, and entirely surrounded by the deltidium and its tubular 

 expansions. A flattened space occurs between the beak ridges and hinge line : valves 

 moderately convex, with a longitudinal sinus in the ventral valve, to which corresponds a 

 mesial fold in the opposite one : external surface entirely smooth when young, and often 

 remaining so to an advanced age: from 10 to 20 short rounded plates ornament the 

 vicinity of the margin ; 3 to 5 occupying the mesial fold and sinus. 



Dimensions variable: length 9, width 12, depth 6 lines; 



>) o, ,, y, >) o ,j 



5, „ 5, „ 2£ ,, {T. lentiformis, Woodward.) 



Obs. Faugas St. Fond appears to have been the first author who figured this form, 

 but without a name. In 181 3, Schlotheim applied to it the denomination of Terebratidites 

 limbatus, referring at the same time to Faugas's figure ; this name is therefore the oldest 

 we are acquainted with, and has aright to priority, as admitted by Prof. Bronn. 



In 1822, the same species was described and figured by Dr. Man tell, under the name of 

 Ter. subplicata, by which denomination it is known to the greater number of British and 

 Foreign Palaeontologists. Dr. Mantell states it to be well characterised by its smooth 



11 



